Processing of electrical condensers



P. E. EDELMAN PROCESSING OF ELECTRICAL CONDENSERS Feb. 14, 1928.

Filed May 11, 1927 I vINVENTOR.

Patented Feb. 14, 1928.

1,658,976 PATENT OFFER.

IfHI'LIY 'EDELMAN, or CHICAGO, ILLINOIS.

PROCESSING or ELECTRICAL CONDENSERS.

=Appli'c ation filed May 11,1927. sriarnorisosss.

'lhis invention-relate'sto the process of manufacturingelectrical-condensers of high capacity, rsrnall,:-bu1k, and -dryi, solid type suitable for: use. in. radio battery eliminator cincuits anthothenelectrical apparatus, and for has :its. objectzjtheproductionvofuniformly gobdi'condensersgof durable quality requiring F no watering: or servicing attention. uffomobtain large 'capacity; in;.-s mall;{;bulk

condensers are unsuitable, as are also; :wet

' condensers; gemployin'g' liquids, pastes, or

jellies therein. Gonfron'ted;,byt11e necessity of preparing =condensersoi .uniform; quality at low; cost I have. :oonceivcd that; they can bev produced electrochemically; in; solid form reseinhlinga rock in hardness and pe'rma'- nently sealed-wfOr use inservice avit-h: free liquid :a'bse'nt ,therein, gthus; preventing the clectrodesthereof from corrosion or-solution into :the active: dielectric ,mat-erial employed;

7 My method-forproducing-such condensers sliouldjhot be confused. with electrolytic wet condensers. using .solutions, or jellies as the-terminalproductas' a solidmass. in texture," affording: Ehigher l capacity, greater dielectric value, -Epermanent -::stability and uniformity -in-- -.pr.oduction.f .-Heretofore electrolytically 1 prepared condensers. have been tlefeatedon the :point oi-durability because no provision :has been made. to prevent the metal electrodes employcdgdissolving into the-solution employed. I have conceived that the-way to avoid this is to remove all free liquid which can react chemically with the metal electrodes during-the processing so that theterminal product is-substantially a solid material with no uncombined moisture or-liquid capal'ile'ofwfurther solvent action thereon. I accomplish-this by employing a chemical mixturepreferably made up from salts which can be prepared as a hot liquid from which interlocking :crystals will form on. cooling and simultaneously passing forming electric current 't-herethrough while crystallization takes place, preferably inrreasing the;voltage at'which the electric current is applied at the time crystallization cc-n'm'iences. I prefer to employ a basic salt mixture containing ammonium and for e1;-

7 .ample may use ammonium phosphate, or

ammonium phosphate mixed with sodium phosphate, or ammonium phosphate mixed with ammonium borate, employing concenrrz-itionsthereof \\'hi(-.h are liquid at high temperature such as 100 degrees C. and becomea solid-mass of'crystals upon cooling down to room temperature.

Various; changes and modifications may be made within. the scope of the appended clainisand Lwill now describe. by way of example. assuitable mode of processing such electrical condensers in ;accordnnce with my invention; H 1 ;j-,Reference jis. madeto' the accompanying drawingsof-avhich the-figure is :1 schematic (lia'gram'illustrating asuit-ablc processing of a condensenitbeing understood-that a plurality; ofcondenserscan be processed simultaneously,-'-additional units beingconnected -to clip v-terminalsi =16. The positive electrode 9 and negative electrode 8 are held in containenlspacedfby'blotter sheets 13 and 14., Innerterminal-4and outer-terminal 5 of sheet; 9 comprise the positive terminal connection for sheet metal 9 andmay be convenientlyiformed at the'respective ends of said sheet9;g ,Similar .-inne1 pand outer stripsB, 2 respectively are formedfrom the ends of negative metal sheet 8 and comprise-the negative terminal. ;An adj ustable rheostat 6 serves to regulate the current flow .from battery 7 ;to terminals 16 which are fastened to strips,;l5,4 and1 -.2,'if respectively. The chemical l'l'inpour pot-12 can thus be applied to impregnate sheets 13, and 14 and co erf-fmetal-sheets 8 and 9 except at the top of terminals-4, 5 and 2, 3 respectively which are subsequently geovered with protective pitclrsealingimaterial as hereinafter set forth-when the container 1 is sealed. A fan 10 can be connected via plug to a supply line to -facilitate cooling of the contents of container 1. j -A condenser consists of electrodes separated by a dielectric material and it is known that the dielectric valuedetermincs the capacity as also does the area of the electrodes and the effective distancetherehetwcen. However in electrochemically formed condensers the distance between electrodes which is effective comprises a minute layer formed on one of the electrodes by the dceompostiion effect of forming electric current sent thru the condenser. I find that the dielectric constant can be greatly increased by operating the condenser at pres;- sure greater than atmospheric pressure, thus forcing the minute layer at the electrode into intimate contact therewith.

I-can make condensers for either high or low -voltage operating service for use in either 13 orA radio power uni-ts. F or example, a condenser suitable for use in an A eliminator device may be prepared-as follows:

thickness are prepared'interleaved'ivitli :two sheet strips of cotton lintcr blotter paper or other suitable absorbeir't--' fibrous material. Terminal strips are taken out at each end of each aluminum strip soth-at electric"'current can be fed theiethiough fronrboth ends of each strip. These stri ps'are substantially wound in conrolutio'ns with-tho blotter paper separating the aluminum strips, making-the outer contour-bf the "winding an elliptical oval shape. =The aluniinu'msheet-s may each comprise a strip 7 inches wide and 8 feet long with the terminal strips thereof' linch wideand 5' inchesj long-at eadh'end' thereof. .he blotter strips may each; comprise-white blotter prepared from c'o'tton linters known in the 'pape'r-Ftra'de a s' 80 pound"'stoclrfsoft rolled grade, 8 inches wide and' tteet long. Two'aluininumstrips' andtwo blotter strips are llS8d" 'fOl" 'e3Ql1-001111611961 'l/Vhen so wound; the aluminum and blotter strips are preferably =pla'e'ed= in'a' container which is proofed *a'ga inst' *t hef destructive action of a hotliquid =and= shaped "to fit the outer contour of'thewinding. Thus "Ior'the above stated winding a pap'e'r-can 9 in'ches high with cross -section"-in 'the farm of an 'GVaI abOutfQ inches wide and ifinches long is suitable when -wotmdwith "five ply paper coated with asplialt-ip'itch, capped with aluminum=end -piece and coated -wit-h a heat resisting-Wink containing-paraflin.

' .The condenser -winding-'is plaeetl 'in the said containerso that-the te'rminal strips project out from the top thereof while the container holds the wintlingiinplace. A-"hot chemical mixture in liquefied 'form is now ponredinto the container to impregnatethe blotter strips therein. This mixture may comprise one part -by volume ()flttl'liniOnium phosphate to eight parts ofsodium-Phosphatc intermixed and heated to boilingpoint with the-a'd'dition-of only a littledistilled water sufiicient-to make up for evaporation loss. occurring during the processing. At about 100 degrees 'cent-igrade a clear hot liquid'results from which the 'topscumthereon caused by impurities may be removed.

This liquid will only'reniai'n in liquid form in currenfat-six to ei ht volts ressure 'is applied between the wound aluminum sheets. Connection from 'a source of directcurrent is made to both the inner'a-nd' outer terminal strips of one aluminum'sheet' at -common potential, so that current'flows well distributed t-llEilCflOIl'l thru the chemical =niass held in the blotter sheets to-the -other aluminum strip which siaulariy has its inner and outer teri L I mine-l ends connected at common potential. 'lwo sheet aluminum strips each of .008"

The forming current thus polarizes one aluminium-str p pos tive and the other remains negative thereto. At first a large current wil'lfiow,lafor example 10 amperes.

However as forming action begins this current will"reduceautomatically to one or two amperes. Atter the c-hemical mixture-begins to cool -sutiiciently so'- that'crystallization commences -as-may be de termined 'by: obeervation I;prefe-r to immediatelyaaisethe voltage at which the forming current is applied. This suddeu change of :applied 'volta'ge greatly reduccs the time r uired :itor formation when applied just-at t e instant crystals begin to form in -the container. The voltage selected should be slightly :higher than the voltage athvhich' thecondenserzisto be-operatedinservice. --For example if ithis condenser is to withstand 12 volts in operating 'serviceyth'e:terminatwoltage applied after crystallization' starts-may be 13 "volts. During -the '=forining iaetion some of :the aluminum combines chemically :with "the chemical ini'irture and energetic bubbling may b'e-observed. It is necessaryipto continue the forming until such bubbling can noilonger beobservd' attwhieh time the chemicalmixture will have become a 'substantiallysolid mass containing .no uncoinbined solvent liquid. The aluminum sheets will thereafter not be able 'to-dissolve in or combine with the chemical mixture to further reduce the thickness-0f the aluminum sheets asthc solid mass becomes highly resistantgtozsuchfurtrochemical, or inolec ularexpansion changes inherent therein. but SUillCIQIIt-QXC-CSS .pressure to burst the container searlris not attained due to the elimination of cxeessliquid from the chemical mixture during the'processing aforesaid. Such a condenser can be employed in a battery eliminator or :other electrical circuit mounted in anyposition, vertical or horizontal as=there is nothing to spill therefrom. It will havehigh capacity of the order of 4000 microfarads, goo-d dielectric strength, and durabilitywith minimum leakage current. The measured dealtage current of such a condenser is of the order of one milliampere at ten volts applied in the correct sense according to the polarization of the condenser. In the reverse direction, a large current can fiow. Such a condenser is very well suited in a circuit for filtering out alternating current fluctuations from rectified current supply. A condenser for service on higher voltage can be similarly prepared except that less area is usually required in the shee-tsused and the chemical mixture is preferably comprised by ammonium phosphate mixed with ammonium borate with the latter'salt in a minority proportion in themixture; Various other chemicals or metal slieets,may"be;*applied in a similar processing as long asftherequisite steps pointed out are observed so that the metal will not be lost; in service by going into solution with the chemical'mixture employed, The formingcurrent should heapplied at a voltage greater thahthe service voltage on which the condenser is to be used and not brought to such value until crystallization has started in thechginical mixture employed.

A condenser for use in a B eliminator may comprise two aluminum strips .1. wide wound 4 interleaved with blotter paper with the "length inches, similarly treated, the chemical mixture used being preterably one part by volume joff am'monium phosphate to one third part by volume of ammonium borate. -Wha tever chemical salts are selected, they should becapable of forming interlocked crystals resembling. a solid mass at roon temperature and not individual or independent separated crystals. I It is advantageous to progressively increase the voltage at which the forming electrical current is applied by increments as the crystallization progresses. If a large mass condenser is to be made this way external cooling may be advantageously applied to hasten the formation of the crystals, as for example an air blast or cold water bath external to the container. In any case it is very advantageous in change the pressure forcing the electric forming current thru the mass at the time when crystallization commences andto continue the flow of forming current until substantially a solid mass of crystal results so that thereafter said crystals have substantially no opportunity to react chemically to destroy the aluminum sheets exposed thereto. A very stable condenser results when this precaution is observed whereas otherwise, an incompletely formed condenser may burst the container in operating service. The container should not be sealed until a substantially rock like mass results therein. lt is important to have the container conform in shape to the outer boundary of the convolut ion winding so as to exert sufiicient mechanical retaining force thereon during service. It is important that-tho forming current'be applied simultaneously as the crystallizationoccurs, if a good condens 19 desired. It is"a'c lvantageous' to have am 'inonium in tl'ie'cheinical mixture employed as'same has a'ben-ficial action on the aluminum sheets-tending to"resist solvent action "of the chemical mixture thereon.

' I'have now setforth the steps of my method of processing condensers. The exact mechanical dimensions are not important as long as the principles set forth are observed. It may be remarked that chemical salts prepared in a solid interlocked'mass in this manner have conductivity properties different than'inthe caseof an'electrolyte consisting largely 'of ,water. The salts in the completed" condenser contain substantially only their'own water of crystallization and nofr'ee uncombined liquid is'presenti The blotter) paper exerts a cooperating action tending to'pr'eservegthe chemical mass at its best operating eificiency. The chemical mass in the blotter paper has conduction characteristics more resembling-the conductivity of a metal conductor than that of a liquid electrolyte and undoubtedly includes a certai'namoun't of aluminum combined electrochemically therewith during the forming proce's's' because a characteristic dark color can be'obsel've'd on the originally white blotter sheets when the condenser is completely formed. This differs from the whitish metallic film noticed on aluminum in electro'lytic wet solution type of condensers.

' I claim: 1 e

'1. The" process of preparing an electrical condenser which consists in subjecting aluminum to the forming action of electric currentin the presence of chemical crystals concentrated as a hot liquid when the electric current is first applied and progressivc ly increasing the voltage maintaining said electric current as crystallization proceeds therein until a substantially solid state is reached thereby.

2. The. process of preparing an electrical condenser which consists in subjecting aluminum sheets to the forming action of electric current in the presence of chemical crys tals concentrated as a. hot liquid with which said aluminum material can react when electric current is first applied and progressive- 1y continuing said electric current under the pressure of increased voltage as said chemical crystalsforinfrom said liquid until a substantially solid crystal mass results therefrom highly resistant to further reaction with said aluminum to an extent which substantially prevents chemical combination of said crystals and aluminum thereafter.

3. The process of preparing a stabilized electrical condenser which consists in passing electric current between aluminum sheets exposed to a chemical mixtur maintained c r e b t e ahmrlim mi' n in qu d-sta e whe tseifl q in liquid state \yhensaid cnrrent is first applied an d el the pressure at .which a d r e is epifi ed m ishew teg crystallization occurs insaid chemical mixture, continuing this treatment until alsulr taetial r cl dmass afa -sea e a es .z emica .mirture aeesxtnt ig 'h substantially ppeyents -f 1i r; ther chemical reaction thereof into..molec ,ular combination with said aluminu nthereafter T p1 .=ess 2 p paie lasteh i e e ect i a se ds-u e of high fiiel 't i value which consists inl foroing for iiing electric eets ,cxposed to ammonitun saltsgmaintamedin liquid s at .-w. nr ei slim-r t fit 5a1 n ie e sing the. voltage at which saidc-ui'rentapplied vhen said ammoni un salts to ys a 'itbe t irqm q at i ie h formingelect-ric 'ourren ntil a sabstant-ially solid-mass ofcryst-als tliro glniql ich electric current cen he t aiten-flo v t e stantilly notnrther solvent actionlof said salts n-said ah -minum... a

h P 9 95 9i n pa esa S abilized electrical condenser 'of h gh "capacityg ivlhicl on n q r iegt smie es 'ie i el between aluminum sheets zexposed tfo a salt mixture containing .ai nnoninni which ai leq i current is arrtkdaaseid cooling ,progresses klown Igto room tempera;

ture, until a substantially solid mass ptciyys- :tals vit-hout ,gtree liquid vresults ,hi gh ly -re- .sistant to further solvent action [,on said aluminum whenelectricaln-currenti ethereafter is passed bet. een said Ialuininum sheets.

.6. The method of producin electrical conlensers which comprises win ing aluminum sheets and blotter. paper in convolutionsi, placing same in a container, .then pouring rhcmicai salts in substantially molten state therein to impregnate said blo ttcr paper therewith, .then passing electrical current between said alunlinum sheets and continuingsaid latter treatment until said salts crystallize as a substantially solid mass therein.

7. The process for making an electrical condenser which comprises sandwiching aluminum shcets and blotter :papenand placing same in a containerproofedagaiixst the thern'lic (lO-tlHCtlQIl of a hot liquid. then pouring a liquefied chen'iical intosai'd containcr to impregnate said blottcr paper therewith. then passing electric current between said aluminmn sheets, then, as crjtstals begin to form in said container increasing the voltat-which said electric currentisnpplicd, continuing this treatment until gasl ubbles are no longer noticed in said container-, and sealing said container contents from the atmosphere thereafter.

ing adjacent sheets lof'nietalfand fibrous ab sorbi ig materialin acontainer, pouring'liot chenncal-ili uefied stash saidcontainer, simultaneoiisly cooling'said salts ,to crystalli ze same' and passing electric current therethroiigh, .0ntinuing the treatment until a substantially .roclglikc mass is attained withentiree liquid jin said container, and then 'is ealingA-heconten'ts of-said container from tl ifiotmosph ere. i pr ncess 'of pioducing a condenser su lt a hle oi radio ')o\1\ e'i" battery cli in inato r fgircnrt s ;which v 569 p'nses' preparing adjagqnqy l 's posed meets offaiiiihiiiuzn and ,tihroti'siahsorliifigf ii teifi al in container into on; led chemical capable'of formll'ltetlqqk l lg .Qi'ystalsi'S pourcd,' solidifymg ,sard; gli einrca l simultaneously passng eleqtr c our-rent, therethrough juntil such igblnfigi? 1 mm 1 s ,subsfi'ntlally no further sollxfgitgacti on thereof :on said aluminum, then sealing. n t a i nleif to maintain the contents theie'iifmiider a"pressure suitable for e service-thereof.andgreatcr than atmor- ,pi rie i i i ;i;l0-..Ili i tor-fl king a re ,eop'deiis e' i'eh conipr' la'cingsh'cets' of .lib rous a eat mater l nd cooperating h M nta,-1ng1', 1)our1ng a hot cge calmrxture n said .COIlttllllQl' and resaid alui11ix1 1m; 1nde1' the ioi electr cu rent-applied initially pre refof about eight volts and finally higher .aolta" e', continuing the treat ii 'til'said clieinical mixture has cooled c'lom i toija uhstantiallyisolid mass includirg hb-[fiQBIlilliiil"other than the self contained water-of crystallization thereof; and theregaifter gcaling said container to maintain a p ress1 i-e tl iere1n higher than atmospheric p es e- 11. {The process for making an electrical c9ndense'r of small bulk and large capacity constructed as a unit of solidity r mbling .a.,rock in hardness winch compr armling ,cginvqlut-ions of metal adjacent. to porous sl1ects ,'holding same in a container, pouring:- a liquid chemical capable of ci stalliziniz ,intosoli d state therein, feeding electric current between said .nietal convolutions so that said.current lion's. in saidmctal from lmth the"-inner andi outer portions of said convolntions midthrough said chemical as crystaljorm tliercin', Whci clg the current density at- Said inner and utcrportions of said conrolutions is approximately equalized, and scaling said container when cr .'.=tallization is completed.

L12 fllhc process for making an electrical condenser of small bulk and large capacity ivhich comprises assembling metal and fibrous sheets in a container, pouring a chemical therein capable of forming interlinked! crystals upon cooling from the liquid state attained when poured, cooling said chemical and simultaneously passing electrical current therethrough, increasing the voltage forcing said electrical current through said chemical after crystallization thereof starts, and terminating said treatment after the contents of said container no longer include free liquid from said chemical.

13. The method and process of making an electrical condenser of small bulk. large capacity, high dielectric strength and stability. which consists in assembling sheets of metal interleaved with fibrous absorbent sheets in a container, impregnating said fibrous sheets 1th aehemical mixture capable of reacting with said metal sheets, simultaneously passing electric current through and crystallizin said chemical mixture to substantially soliu form resembling a rock in hardness and incapable of dissolving action on said metal sheets after reaching said solid form, and thereafter sealing said container from the atmosphere to permit its contents to operate under a pressure which is difl'lerent than atmospheric pressure,

14. The method of and process; of making an electrical condenser of small hulk, large capacity. high dielectric strength, and sta bility which consists in winding sheets of aluminum alternated with sheets of blotter paper so that the outer contour of said wind ing resembles an elliptical oval, bringing out inner and outer terminals from the respective inner and outer ends of each alin'ninum sheet, placing said winding in a Container. pouring liquefied salts containing ammonium therein, feeding electric current through said salts in said container while maintaining both he inner and outer attire-- said terminals of (I-.Cl. particular alum num sheet at comm n potential whereby IEPPI'UXlmatcly uniformly distributed current density is maintained at each instant of time 11012 the surface of each particular sheet of aluminum, crystallizing said chemical salts and increasing the electrical current flow tin-rcthrough during the time when crystallization commences, and sealing the contents of said container from the atmosphere after crystallization is substantially completed.

In witness whereof I have hereunto set my hand this 7th day of May, 1927.

PHILIP E. EDELMAN. 

